55 free tools, all running in your browser
Professional online tools that never see your data
Format JSON, convert files, edit images and more. Every tool runs in your browser, so your data stays on your device. Free, fast, no sign-up.
Browse by category
Pick a category, then pick a tool. Each one has its own page you can bookmark.
Developer tools Format, validate, encode and inspect data 20 live Text tools Count, clean, convert and transform text 8 live Image tools Compress, convert, resize and edit images 6 live PDF tools Merge, split, compress and convert PDFs 5 live Converters Units, colours, number bases and data formats 9 live Calculators Percentages, dates, loans and everyday maths 7 live
Ready to use now
Each tool is free, runs locally and has a guide underneath it.
JSON Editor Two panels with text, tree and table modes, compare, transform and repair JSON Formatter Pretty print messy JSON with your preferred indentation JSON Validator Find the exact line and character of any JSON syntax error JSON Minifier Strip whitespace to shrink JSON for production Code Formatter Beautify JavaScript, TypeScript, CSS, HTML and SQL Text Diff Checker Compare two texts and highlight every difference Image Editor Crop, resize, rotate and export images in your browser PDF Converter Turn images into a PDF or merge PDFs, all offline JSON to CSV Flatten JSON arrays into a clean CSV spreadsheet JSON to YAML Convert JSON to clean, readable YAML YAML to JSON Turn YAML into JSON and catch indentation mistakes XML Formatter Pretty print and validate XML, SVG and XHTML Base64 Encode / Decode Encode text or files to Base64 and back URL Encode / Decode Percent-encode or decode URLs and query strings JWT Decoder Inspect JWT header, payload and expiry without a server Regex Tester Live-match regular expressions with group highlighting UUID Generator Generate one or thousands of v4 UUIDs Hash Generator Hash text or files with MD5, SHA-1, SHA-256 and SHA-512 HTML Entity Encoder Escape and unescape HTML entities safely Timestamp Converter Convert Unix timestamps to dates and back, any timezone Cron Expression Parser Translate cron schedules into plain English and next run times Word Counter Words, characters, sentences, reading time and keyword density Case Converter Switch between upper, lower, title, sentence, camel and snake case Lorem Ipsum Generator Paragraphs, sentences or words of placeholder text Markdown Preview Write Markdown on the left, see rendered HTML on the right Slug Generator Turn any title into a clean, SEO-friendly URL slug Remove Duplicate Lines Deduplicate, trim and clean lists in seconds Sort Lines Sort lines A to Z, Z to A, by number or by length Text to Binary Convert text to binary, hex or octal and back Find and Replace Bulk find and replace with plain text or regex Image Compressor Shrink images up to 80% with a live quality preview Image Converter Convert between PNG, JPG, WebP and AVIF in bulk Image Resizer Resize by pixels, percentage or preset social sizes Favicon Generator Every favicon size and the HTML to go with it from one image Color Picker from Image Click any pixel to get its HEX, RGB and HSL values PDF Split Extract pages or split a PDF into separate files PDF Compress Reduce PDF file size by recompressing images PDF to Image Render PDF pages to PNG or JPG at any resolution PDF Page Reorder Drag pages to reorder, rotate or delete them Unit Converter Length, weight, temperature, area, volume and speed Percentage Calculator What is X% of Y, percent change and more, with the working Loan & EMI Calculator Monthly payment, total interest and a full schedule Age Calculator Exact age today or on any date, down to the day Date Difference Calculator Days, weeks, months and years between any two dates BMI Calculator Body mass index with category and healthy weight range Tip Calculator Tip amount, total and per-person share in one tap Color Converter Convert colours between HEX, RGB, HSL and OKLCH Number Base Converter Convert between binary, octal, decimal and hexadecimal SQL Formatter Format SQL for MySQL, PostgreSQL, SQLite and SQL Server GraphQL Formatter Format and validate GraphQL queries and schemas Mock JSON Generator Generate realistic fake JSON from a simple schema API Request Tester Send GET, POST and other requests and inspect the response Password Generator Strong random passwords and passphrases, generated locally QR Code Generator QR codes for URLs, Wi-Fi, contacts and text as SVG or PNG Compound Interest Calculator Growth over time with contributions and a yearly chart
Built the way a tool site should be
No upload forms, no email gates, no ads on top of the tool. Just the tool.
Private by design
Every tool runs in your browser. Nothing you paste or drop is uploaded, logged or stored.
Instant
No page reloads, no queues, no waiting for a server. Results appear as you type.
Free, no sign-up
No account, no trial, no limits. Open a tool and use it.
Works offline
Once a tool has loaded it keeps working without a connection. Install Cuisdev as an app.
Mobile friendly
Every tool is designed for a phone screen as carefully as for a desktop.
Open and documented
Each tool explains what it does, how to use it and the mistakes it catches.
From the blog
What is CORS and how to fix CORS errors CORS errors explained in plain terms, why the browser blocks the response, what preflight requests are, and how to fix the server, not the client. Cron syntax explained with 30 real-world examples Cron syntax explained field by field, with 30 copy-ready cron examples for every minute, hourly, daily, weekdays, monthly and the gotchas that break schedules. JWT explained: structure, signing and security mistakes What a JSON Web Token is, how its three parts and signature work, HS256 vs RS256, and the JWT security mistakes that lead to real vulnerabilities.
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